Dreams in Ancient Medicine

I. Dreams in the Ancient World

Along with many people before and since, most Greeks and Romans believed that dreams could give information about past, present, and even future events. Dreams, however, are manifestly not records or transcriptions of these events. Dreams demand interpretation.

Even when interpreted, some dreams will prove to be false; first of all, therefore, the interpreter must decide how to distinguish true dreams from false, as Penelope does at Odyssey xix.560 ff. She suggests that dreams can be distinguished according to the path by which they reach us; true dreams pass into our consciousness through a gate of burnished horn, while deceptive dreams enter our world through a gate of ivory. The need to distinguish true dreams from false leads naturally to consideration of the causes and mechanisms of dreaming.

Dreams could be caused by external factors like a god, a ghost, or a daemon, or by internal factors like the dreamer's own soul, recollection of waking activities, or physiological state. Plato recognized that dreams were one of the ways by which the gods conveyed their intentions to mankind (Apology 33c); at the same time, he allows that natural causes, including disturbances in the body's internal motions, can give rise to dreams (Timaeus 45e).

Around these fundamental polarities of true vs. false and divine vs. natural, ancient philosophers, writers, and theorists of all kinds organized their thought about dreams. For most people, the most important function of dreams was to predict the future, and the first step in interpreting dreams was to recognize which dreams were both god-sent and true. Aristotle's agnostic attitude toward the possibility of prophesy through dreams (On Dreams 462b12-17) marks an exception to this general rule, as does the Epicurean dogma that "Dreams have no divine nature nor any prophetic force but originate from the impact of images" on the senses (Epicurus, Vatican Sayings 24).

II. Dreams in Ancient Medicine

Medical writers also took an interest in the distinction between divine and natural dreams; for the most part, however, they were interested in the dreams that were both natural and true, from which a physician could gain information about bodily states and processes that were hidden from direct observation. The earliest extant Greek treatise on dreams happens to be a medical work: the fourth book of the Hippocratic treatise On Regimen, from the end of the fifth or beginning of the fourth century. The author of this treatise stakes out for himself the territory left by the diviners' uncertainty:

Whatever dreams are divine and foretell evil or good to communities or to private persons have interpreters who are in possession of an art concerning such matters. But whatever physical symptoms the soul foretells – surfeit, depletion, excess of what is natural, change to what is unaccustomed–these things, too, have intepreters, and sometimes they chance to get it right, but at other times they miss the mark. (On Regimen 4.87)

The author of On Regimen 4 claims to offer a true account of the dreams that foretell physiological events. This account of such natural dreams combines explanation of their causes with suggested interpretations of their meaning.

In its concern with causes, however, On Regimen 4 is anomalous in the literature of ancient medicine. Most medical writers and schools, with the prominent exception of Galen, did not concern themselves with the aetiology or mechanism of dreams. Instead, they used dreams as a diagnostic and prognostic tool without committing themselves to any explanation of how or why dreams reflected physiological reality. It was enough to accept that a patient's dreams might be part of the ensemble of information that the physician brought to bear in his attempt to construct an account of the patient's condition, and an appropriate therapy for it.

Modern scholars, following Galen's lead, often speak of three or more medical sects or schools in Roman medicine: dogmatists, empiricists, and Methodists. Some speak also of an eclectic school, whose chief representative is Galen himself. Only the Methodists, however, could claim to be a genuinely self-defined sect, with a founder and distinct medical theory. "Dogmatist" and "empiricist," like "liberal" and "conservative" in American politics, refer to tendencies of thought, not clearly defined doctrines, and in practice the therapies of dogmatist and empiricist physicians probably resembled each other more than they differed. In evaluating dreams, however, these two schools at least stood apart from the Methodists.

According to Galen (On the Natural Faculties I.12), the Methodists rejected dreams and other forms of divination as indicators for diagnosis or therapy. Empiricist physicians, who rejected theory of all kind and based their practice on experience, accepted the possibility that dreams, like any other experience, might point to useful therapeutic practices. No indication seems to have survived of the dogmatists' attitude toward medical dreams, but there is no reason to believe that they denied their utility.

Divine dreams are another matter. Those that came from Asclepius or other healing gods play an especially prominent role in Greco-Roman medicine. These dreams, which the sick eagerly solicited at shrines like those at Pergamum or Ephesus, had by their very nature a claim to be regarded as both god-sent and true, and thus distinct from the natural dreams that were the province of physicians. For the ordinary patient, messages from a healing god were one among many available sources of medical knowledge. The Sacred Tales or Hieroi Logoi of the rhetorician Aelius Aristides (2nd century A.D.) present an extreme example of one highly educated patient's faith in healing dreams and in Asclepius as something like a personal savior; more typical, perhaps, are the cures recorded in a series of inscriptions from the sanctuary of Asclepius at Epidauros.

These inscriptions were set up on a series of tablets or stelae in the sanctuary; six of them were seen by Pausanias in the second century A.D. (Descriptio Graeciae II.27,3 = Edelstein & Edelstein T384, p. 195). The tablets describe miraculous cures performed by Asclepius. Not all the cures involve sleep; in one, for example, a voiceless boy is cured immediately after performing the preliminary sacrifices to Asclepius; in another, a growth on a boy's neck is healed when one of the temple dogs licks it. These are exceptions, however, and the vast majority of cures recorded on the stelae come after the ailing suppliants have slept in the sanctuary in hopes of a cure. This practice is called "incubation."

Some of the Epidauros suppliants see a "vision" (opsis), others a "vision-in-sleep" (enhypnion) – the word used by Galen in On Diagnosis from Dreams. Still others appear to have a direct encounter with the god, like that of a certain Euhippus, who had lived for six years with the point of a spear embedded in his jaw.

As he was sleeping in the temple the god extracted the spearhead and gave it to him into his hands. When day came Euhippus departed cured, and he held the spearhead in his hands. (Inscriptiones Graecae IV 2, 1 = Edelstein & Edelstein T423, 232).

In a few cases, the patient is cured after sleeping in the shrine, but no mention is made of a dream or vision.

Finally, it is important to avoid the temptation to construct a tidy scheme in which divine dreams are the province of faith healers and natural dreams a tool of rational physicians. The dichotomy between divine and natural dreams does not correspond exactly to the distinction between rational medicine and divine healing, and in fact that distinction was far from absolute in Greco-Roman medicine. Galen, to give only one example, records with apparent agreement the case of a wealthy man who came to the shrine of Asclepius at Pergamum and was cured there by a dream from Asclepius (Subfiguratio Empirica 10,78 Deichgräber = Edelstein & Edelstein T436, p. 250) and acknowledges his own cure at the hands of the god (De Libris Propriis 2 = Edelstein & Edelstein T458, p. 263).